Linnaeus’s two-toed sloth, or otherwise known as Unau, is thought to be the slowest mammal in the world. The coloration of this animal's fur varies from gray-brown to beige with characteristic greenish cast as a result of algae, growing in the fur. The outer layer of its fur is long and bristly, while the under layer is made up of shorter, finer hairs. Unlike in other mammals, Unau's coat grows from its stomach to the back. On its hind legs, Linnaeus’s sloth exhibits 3 toes, whereas forelegs of the animal have only 2 webbed toes. Unau is a very light-weight animal as compared to other mammals of its size. This helps the animal collect leaves from long, thin branches.
The range of Linnaeus’s sloth stretches through the Central America and northern South America and some parts of Brazil and Peru. The preferred habitat of this species is high canopy of the tropical rain forest. Home range of each individual is usually about 10 acres.
Linnaeus’s sloths are usually solitary animals, although females can sometimes be feeding in the same tree. These animals spend as much as 15 - 20 hours per day sleeping. They wake up at night to feed, moving to a new tree each night, but rarely passing more than 40 meters. Most of the time is spent hanging upside down in trees. They use their long claws to cling onto branches of trees. Young often inherit home ranges of their parents. When on land, Linnaeus’s sloths are very clumsy. However, when in the water, they prove to be accomplished swimmers, using their long arms to move through water. Unaus are generally silent animals. However, when threatened, they are known to emit hissing sounds, low cries and moans. Their main tool of self-defense is camouflage, although claws and teeth also allow these animals to defend themselves.
Linnaeus’s sloths are primarily herbivores. Their diet mainly consists of berries, leaves, small twigs, fruits and other vegetation, complemented with small prey such as insects. The typical matter of feeding is harvesting leaves with their lips.
Little is known about the mating system of Linnaeus’s sloths. However, it is suggested that they may exhibit either polygynous or polygynandrous (promiscuous) mating systems, and females appear to initiate mating. Linnaeus’s sloths mate year-round. According to observations, these animals may have a peak season, occurring in March-April. Females of this species produce young once a year. Gestation period lasts for 6 months, yielding a single baby, which lives clinging into the belly of its mother for the first 5 weeks of its life. Independence is reached at 1 year old, although the young sloth often continues to associate with its mother until 2 years old. Age of sexual maturity is 3 years old for females and 4 - 5 years old for males.
The biggest threat to the overall population of this species is habitat destruction as a result of hunting for their coat, meat and claws as well as logging of their rainforest range. As extremely slow animals, Linnaeus’s sloths are often hit by cars on roads, passing through forests, which they inhabit.
According to IUCN, the Linnaeus’s two-toed sloth is widely distributed but no overall population estimate is available. Currently, this species is classified as Least Concern (LC) on the IUCN Red List.